U.S. patent number 7,518,893 [Application Number 11/826,480] was granted by the patent office on 2009-04-14 for method for operation of a converter circuit, as well as an apparatus for carrying out the method.
This patent grant is currently assigned to ABB Schweiz AG. Invention is credited to Srinivas Ponnaluri, Jurgen Steinke.
United States Patent |
7,518,893 |
Ponnaluri , et al. |
April 14, 2009 |
Method for operation of a converter circuit, as well as an
apparatus for carrying out the method
Abstract
A method for operation of a converter circuit is specified,
wherein the converter circuit has a converter unit with a
multiplicity of drivable power semiconductor switches and an LCL
filter which is connected to each phase connection of the converter
unit, in which method the drivable power semiconductor switches are
driven by means of a drive signal which is formed from reference
voltages. The reference voltages are formed by subtraction of
damping voltages from reference-phase connection voltages, with the
damping voltages being formed from filter capacitance currents,
weighted with a variable damping factor of the LCL filter. An
apparatus for carrying out the method is also specified.
Inventors: |
Ponnaluri; Srinivas
(Untersiggenthal, CH), Steinke; Jurgen (Albbruck,
DE) |
Assignee: |
ABB Schweiz AG (Baden,
CH)
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Family
ID: |
34979360 |
Appl.
No.: |
11/826,480 |
Filed: |
July 16, 2007 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20070263418 A1 |
Nov 15, 2007 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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PCT/CH2005/000293 |
May 24, 2005 |
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60646544 |
Jan 25, 2005 |
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Current U.S.
Class: |
363/62; 363/163;
363/44; 363/56.1 |
Current CPC
Class: |
H02M
1/12 (20130101); H02M 3/158 (20130101); H02M
7/53871 (20130101); H02J 7/345 (20130101) |
Current International
Class: |
H02M
3/06 (20060101); H02M 5/275 (20060101) |
Field of
Search: |
;363/44,56.1,56.11,56.12,62,163 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Other References
Bojrup M et al: "A Multiple Rotating Integrator Controller for
Active Filters" 8th European conference on Power Electronics and
Applications. Lausanne CH, Sep. 7-9, 1999, EPE. European conference
on Power Electronics and Applications, Brussls : EPE Association
BE, vol. Conf. 8, Sep. 7, 1999, pp. 1-9, XP00878439. cited by other
.
Bojrup M et al: "A dual purpose batter charger for electric
vehicles" Power Electronics Specialist Conference, 1998. PESC 98
Record. 29th Annual IEEE Fukuoka, Japan May 17, 1998 New York, NY,
USA,IEEE, US vol. 1, May 17, 1998, pp. 565-570, XP010294935. cited
by other .
Lee S J et al: "A harmonic reference frame based current controller
for active filter" Applied Power Electronics Conference and
Exposition, 2000. APEC 2000. Fifteenth Annual IEEE New Orleans, LA,
USA Feb. 6-10, 2000, Piscataway, NJ, USA,IEEE, US, vol. 2, Feb. 6,
2000, pp. 1073-1078, XP010371636. cited by other .
Teodorescu R et al: "A stable three-phase LCL-filter based active
rectifier without damping" Conference Record of the 2003 IEEE
Industry Applications Conference. 38th. IAS Annual Meeting. Salt
Lake City, UT, Oct. 12-16, 2003, Conference Record of the IEEE
Industry Applications Conference. IAS Annual Meeting, New York, NY:
IEEE, US, vol. vol. 3 of 3. conf. 38, Oct. 12, 2003, pp. 1552-1557,
XP010676201. cited by other .
Macken K J et al: "Distributed control of renewal generation units
with integrated active filter" PESC'03. 2003 IEEE 34th. Annual
Power Electronics Specialists Conference. Conference Proceedings.
Acapulco, Mexico, Jun. 15-19, 2003, Annual Power Electronics
Specialists Conference, New York NY: IEEE, US, vol. vol. 4 of 4,
Conf. 34, Jun. 15, 2003, pp. 741-747, XP010648902. cited by other
.
Dahono, A Control Method to Damp Oscillation in the Input LC
Fileter of AC-DC PWM Converters IEEE, 2002, pp. 1630-1635. cited by
other .
International Search Report. cited by other .
International Preliminary Report on Patentability (IPRP) from the
corresponding International Application No. PCT/CH2005/000293.
cited by other.
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Primary Examiner: Han; Jessica
Assistant Examiner: Pham; Emily
Attorney, Agent or Firm: Buchanan Ingersoll & Rooney
PC
Parent Case Text
RELATED APPLICATIONS
This application claims priority under 35 U.S.C. .sctn.119 to U.S.
Provisional Application 60/646,544 filed in USA on Jan. 25, 2005,
and as a continuation application under 35 U.S.C. .sctn.120 to
PCT/CH2005/000293 filed as an International Application on May 24,
2005, designating the U.S., the entire contents of which are hereby
incorporated by reference in their entireties.
Claims
What is claimed is:
1. A method for operation of a converter circuit, in which the
converter circuit has a converter unit with a multiplicity of
drivable power semiconductor switches and an LCL filter which is
connected to each phase connection of the converter unit, in which
the drivable power semiconductor switches are driven by means of a
drive signal (S) which is formed from reference voltages (u*.sub.1,
u*.sub.2, u*.sub.3), wherein the reference voltages (u*.sub.1,
u*.sub.2, u*.sub.3) are formed by subtraction of damping voltages
(u.sub.d1, u.sub.d2, u.sub.d3) from reference-phase connection
voltages (u*.sub.i1, u*.sub.i2, u*.sub.i3), with the damping
voltages (u.sub.d1, u.sub.d2, u.sub.d3) being formed from filter
capacitance currents (i.sub.Cf1, i.sub.Cf2, i.sub.Cf3), weighted
with a variable damping factor (K.sub.f) of the LCL filter, and
wherein the filter capacitance currents (i.sub.Cf1, i.sub.Cf2,
i.sub.Cf3) are filtered by means of a high-pass filter, wherein the
reference-phase connection voltages (u*.sub.i1, u*.sub.i2,
u*.sub.i3) are formed from a d-component of the Park-Clarke
transformation (produced by regulation of a dc voltage (u.sub.dc)
of a capacitive energy store which is connected to the converter
unit (1) at a dc voltage reference value (u*.sub.dc) of
reference-phase connection currents (i*.sub.fid) and from a
predeterminable q-component of the Park-Clarke transformation of
the reference-phase connection currents (i*.sub.fiq).
2. The method as claimed in claim 1, wherein the d-component of the
Park-Clarke transformation of reference-filter output voltages
(u*.sub.gd) is produced by regulation of the d-component of the
Park Clarke transformation of phase connection currents (i.sub.fid)
at the sum of the d-component of the Park-Clarke transformation of
the reference-phase connection currents (i*.sub.fid) and a
d-component of the Park-Clarke transformation of at least one
harmonic of filter output currents (i*.sub.fghd) with respect to
the fundamental of the filter output currents (i.sub.fg1,
i.sub.fg2, i.sub.fg3), and wherein the q-component of the
Park-Clarke transformation of the reference-filter output voltages
(u*.sub.gq) is produced by regulation of the q-component of the
Park-Clarke transformation of the phase connection currents
(i.sub.fiq) at the sum of the q-component of the Park-Clarke
transformation of the reference-phase connection currents
(i*.sub.fiq) and a q-component of the Park-Clarke transformation of
at least one harmonic of the filter output currents (i*.sub.fghq)
with respect to the fundamental of the filter output currents
(i.sub.fg1, i.sub.fg2, i.sub.fg3).
3. The method as claimed in claim 2, wherein the d-component of the
Park-Clarke transformation of the reference-phase connection
voltages (u*.sub.id) is produced by the sum of the d-component of
the Park-Clarke transformation of the reference-filter output
voltages (u*.sub.gd) and the d-component of filter output voltages
(u.sub.gd) and a d-component of the Park-Clarke transformation of
at least one harmonic of the filter output voltages (u*.sub.ghd),
and wherein the q-component of the Park-Clarke transformation of
the reference-phase connection voltages (u*.sub.iq) is produced by
the sum of the q-component of the Park-Clarke transformation of the
reference-filter output voltages (u*.sub.gq) and the q-component of
the Park-Clarke transformation of the filter output voltages
(u.sub.gq) and a q-component of the Park-Clarke transformation of
at least one harmonic of the filter output voltages
(u*.sub.ghq).
4. The method as claimed in claim 3, wherein the reference-phase
connection voltages (u*.sub.i1, u*.sub.i2, u*.sub.i3) are produced
by inverse Park-Clarke transformation of the d-component of the
Park-Clarke transformation of the reference-phase connection
voltages (u*.sub.id) and the q-component of the Park-Clarke
transformation of the reference-phase connection voltages
(u*.sub.iq).
5. An apparatus for carrying out a method for operation of a
converter circuit, in which the converter circuit has a converter
unit with a multiplicity of drivable power semiconductor switches
and an LCL filter which is connected to each phase connection of
the converter unit, having a regulation device which is used for
production of reference voltages (u*.sub.1, u*.sub.2, u*.sub.3) and
is connected via a drive circuit for formation of a drive signal
(S) to the drivable power semiconductor switches, wherein the
regulation device has a first calculating unit for formation of
reference voltages (u*.sub.1, u*.sub.2, u*.sub.3) from the
subtraction of damping voltages (u.sub.d1, u.sub.d2, u.sub.d3) from
reference-phase connection voltages (u*.sub.i1, u*.sub.i2,
u*.sub.i3), with the first calculation unit being supplied with
reference-phase connection voltages (u*.sub.i1, u*.sub.i2,
u*.sub.i3) and, in order to form the damper voltages (u.sub.d1,
u.sub.d2, u.sub.d3), filter capacitance currents (i.sub.Cf1,
i.sub.Cf2, i.sub.Cf3) of the LCL filters, and a regulator unit,
with the filter capacitance currents (i.sub.Cf1, i.sub.Cf2,
i.sub.Cf3) being filtered by means of a high-pass filter, wherein
the regulator unit has a first proportional-integral regulator to
whose input side the difference between a dc voltage (u.sub.dc) of
a capacitive energy store, which is connected to the converter unit
and a dc voltage reference value (u*.sub.dc) are supplied, and on
whose output side a d-component of the Park-Clarke transformation
of reference-phase connection currents (i*.sub.fid) is
produced.
6. The apparatus as claimed in claim 5, wherein the regulator unit
has a second proportional-integral regulator, to whose input side
the difference between the sum of the d-component of the
Park-Clarke transformation of the reference-phase connection
currents (i*.sub.fid) and a d-component of the Park-Clarke
transformation of at least one harmonic of the filter output
currents (i*.sub.fghd) with respect to the fundamental of filter
output currents (i.sub.fg1, i.sub.fg2, i.sub.fg3) and the
d-component of the Park-Clarke transformation of the phase
connection currents (i.sub.fid) are supplied, and on whose output
side the d-component of the Park-Clarke transformation of the
reference-filter output voltages (u*.sub.gd) is produced, and
wherein the regulator unit has a third proportional-integral
regulator, to whose input side the difference between the sum of
the q-component of the Park-Clarke transformation of the
reference-phase connection currents (i*.sub.fiq) and a q-component
of the Park-Clarke transformation of at least one harmonic of the
filter output currents (i*.sub.fghq) with respect to the
fundamental of the filter output currents (i.sub.fg1, i.sub.fg2,
i.sub.fg3) and the q-components of the Park-Clarke transformation
of the phase connection currents (i.sub.fiq) are supplied, and on
whose output side the q-component of the Park-Clarke transformation
of the reference-filter output voltages (u*.sub.gq) is
produced.
7. The apparatus as claimed in claim 6, wherein the regulator unit
has a first adder for production of the d-component of the
Park-Clarke transformation of the reference-phase connection
voltages (u*.sub.id), to which the d-component of the Park-Clarke
transformation of the reference-filter output voltages (u*.sub.gd),
the d-component of filter output voltages (u.sub.gd) and a
d-component of the Park-Clarke transformation of at least one
harmonic of filter output voltages (u*.sub.ghd) are supplied, and
wherein the regulator has a second adder for production of the
q-component of the Park-Clarke transformation of the
reference-phase connection voltages (u*.sub.iq), to which the
q-component of the Park-Clarke transformation of reference-filter
output voltages (u*.sub.gq), the q-component of the Park-Clarke
transformation of filter output voltages (u.sub.gq) and a
q-component of the Park-Clarke transformation of at least one
harmonic of the filter output voltages (u*.sub.ghq) are
supplied.
8. The apparatus as claimed in claim 7, wherein the regulator unit
has a calculation unit for formation of the reference-phase
connection voltages (u*.sub.i1, u*.sub.i2, u*.sub.i3) by inverse
Park-Clarke transformation, to whose input side the d-component of
the Park-Clarke transformation of the reference-phase connection
voltages (u*.sub.id) and the q-component of the Park-Clarke
transformation of the reference-phase connection voltages
(u*.sub.iq) are supplied.
9. The apparatus as claimed in claim 5, wherein the regulation
device has a second calculation unit for the formation of a
d-component of the Park-Clarke transformation of at least one
harmonic of filter output currents (i*.sub.fghd) with respect to
the fundamental of the filter output currents (i.sub.fg1,
i.sub.fg2, i.sub.fg3), of a q-component of the Park-Clarke
transformation of at least one harmonic of filter output currents
(i*.sub.fghq) with respect to the fundamental of the filter output
currents (i.sub.fg1, i.sub.fg2, i.sub.fg3), of the d-component of
the Park-Clarke transformation of the at least one harmonic of
reference-filter output voltages (u*.sub.ghd) and of the
q-component of the Park-Clarke transformation of the at least one
harmonic of reference-filter output voltages (u*.sub.ghq), with the
input side of the second calculation unit being supplied with the
d-component of the filter output voltages (u.sub.gd), with the
q-component of the filter output voltages (u.sub.gq), the phase
connection currents (i.sub.fi1, i.sub.fi2, i.sub.fi3), the filter
capacitance currents (i.sub.Cf1, i.sub.Cf2, i.sub.Cf3) and the
fundamental angle (.omega.t) of filter output voltages (u.sub.g1,
u.sub.g2, u.sub.g3).
10. The apparatus as claimed in claim 9, wherein the regulation
device has a third calculation unit for formation of the
d-component of the Park-Clarke transformation of the filter output
voltages (u.sub.gd), of the q-component of the Park-Clarke
transformation of the filter output voltages (u.sub.gq) and of the
fundamental angle (.omega.t) of the filter output voltages
(u.sub.g1, u.sub.g2, u.sub.g3), with the input side of the third
calculation unit being supplied with filter output voltages
(u.sub.g1, u.sub.g2, u.sub.g3) of the LCL filters.
11. The apparatus as claimed in claim 8, wherein the regulation
device has a second calculation unit for the formation of a
d-component of the Park-Clarke transformation of at least one
harmonic of the filter output currents (i*.sub.fghd) with respect
to the fundamental of the filter output currents (i.sub.fg1,
i.sub.fg2, i.sub.fg3), of a q-component of the Park-Clarke
transformation of at least one harmonic of the filter output
currents (i*.sub.fghq) with respect to the fundamental of the
filter output currents (i.sub.fg1, i.sub.fg2, i.sub.fg3), of the
d-component of the Park-Clarke transformation of the at least one
harmonic of the reference-filter output voltages (u*.sub.ghd) and
of the q-component of the Park-Clarke transformation of the at
least one harmonic of the reference-filter output voltages
(u*.sub.ghq), with the input side of the second calculation unit
being supplied with the d-component of the filter output voltages
(u.sub.gd), with the q-component of the filter output voltages
(u.sub.gq), the phase connection currents (i.sub.fi1, i.sub.fi2,
i.sub.fi3), the filter capacitance currents (i.sub.Cf1, i.sub.Cf2,
i.sub.Cf3) and the fundamental angle (.omega.t) of the filter
output voltages (u.sub.g1, u.sub.g2, u.sub.g3).
Description
TECHNICAL FIELD
The disclosure relates to the field of power electronics, and is
based on a method for operation of a converter circuit, as well as
an apparatus for carrying out the method.
BACKGROUND INFORMATION
Known converter circuits have a converter unit with a multiplicity
of drivable power semiconductor switches, which are connected in a
known manner in order to switch at least two switching voltage
levels. An LCL filter is connected to each phase connection of the
converter unit. A capacitive energy store is also connected to the
converter unit, and is normally formed by one or more capacitors.
An apparatus is provided for operation of the converter circuit,
which apparatus has a regulation device for production of reference
voltages and is connected via a drive circuit for formation of a
drive signal from the reference voltages to the drivable power
semiconductor switches. The power semiconductor switches are thus
driven by means of the drive signal.
The converter circuit mentioned above is subject to the problem but
the LCL filters can cause permanent distortion, that is to say
undesirable oscillations, in the filter output currents and filter
voltages, resulting from resonant oscillations of the LCL filters.
In an electrical ac voltage supply system, which is typically
connected to the filter outputs, or in an electrical load which is
connected to the filter outputs, such distortion can lead to damage
or even destruction, and is therefore very undesirable.
SUMMARY
A method is disclosed for operation of a converter circuit, by
means of which it is possible to actively damp distortion, caused
by LCL filters connected to the converter circuit, in the filter
output currents and filter output voltages. An apparatus is
disclosed, by means of which the method can be carried out in a
particularly simple manner.
The converter circuit has a converter unit with a multiplicity of
drivable power semiconductor switches, and an LCL filter which is
connected to each phase connection of the converter unit. In an
exemplary method for operation of the converter circuit, the
drivable power semiconductor switches are now driven by means of a
drive signal which is formed from reference voltages. According to
the disclosure, the reference voltages are formed from the
subtraction of damping voltages from reference-phase connection
voltages, with the damping voltages being formed from filter
capacitance currents (which are weighted with a variable damping
factor) of the LCL filters. The damping voltages are thus
proportional to the filter capacitance currents and are then
subtracted from the reference-phase connection voltages, which is
equivalent to connection of a damping resistance to each phase
connection of the converter unit. Distortion, that is to say
undesirable oscillations, in the filter output currents and filter
output voltages can therefore advantageously be actively damped, so
that this type of distortion is greatly reduced and, in the ideal
case, is very largely suppressed. A further advantage of the
exemplary method is that there is no need to connect any discrete,
highly space-consuming damping resistor, which is complex to
provide and is therefore expensive, to each phase connection in
order to allow the undesirable distortion to be effectively
damped.
An exemplary apparatus for carrying out the method for operation of
the converter circuit has a regulation device which is used to
produce reference voltages and is connected via a drive circuit for
formation of a drive signal to the drivable power semiconductor
switches. According to the disclosure, the regulation device has a
first calculating unit for formation of reference voltages from the
subtraction of damping voltages from reference-phase connection
voltages, with the first calculation unit being supplied with
reference-phase connection voltages and, in order to form the
damper voltages, filter capacitance currents of the LCL filters.
Furthermore, the regulation device has a regulator unit for
production of the reference-phase connection voltages. The
exemplary apparatus for carrying out the method for operation of
the converter circuit can thus be implemented very easily and
cost-effectively, since the circuit complexity can be kept
extremely low and, furthermore, only a small number of components
are required to construct it. The exemplary method can thus be
carried out particularly easily by means of this apparatus.
BRIEF DESCRIPTION OF THE DRAWINGS
These and further objects, advantages and features of the invention
will become evident from the following detailed description of
exemplary embodiments of the invention, in conjunction with the
drawing. In the figures:
FIG. 1 shows one exemplary embodiment of an apparatus for carrying
out an exemplary method for operation of a converter circuit,
FIG. 2 shows one exemplary embodiment of a second calculation
unit,
FIG. 3 shows a waveform of the filter output currents with active
damping using an exemplary method, and
FIG. 4 shows a waveform of the filter output currents with active
damping and additional active reduction of harmonics using an
exemplary method.
The reference symbols used in the drawing, and their meanings, are
listed in a summarized form in the list of reference symbols. In
principle, identical parts are provided with the same reference
symbols in the figures. The described exemplary embodiments
represent examples of the subject matter of the invention, and have
no restrictive effect.
DETAILED DESCRIPTION
FIG. 1 shows one exemplary embodiment of an apparatus for carrying
out an exemplary method for operation of a converter circuit. As
shown in FIG. 1, the converter circuit has a converter unit 1 with
a multiplicity of drivable power semiconductor switches and an LCL
filter 3, which is connected to each phase connection 2 of the
converter unit 1. Each LCL filter 3 accordingly has a first filter
inductance L.sub.fi, a second filter inductance L.sub.fg as well as
a filter capacitance C.sub.f, with the first filter inductance
L.sub.fi being connected to the associated phase connection 2 of
the converter unit 1, to the second filter inductance L.sub.fg and
to the filter capacitance C.sub.f. Furthermore, the filter
capacitances C.sub.f of the individual LCL filters 3 are connected
to one another. Each LCL filter 3 typically has a virtually
negligible filter resistance R.sub.f, which is connected in series
with the filter capacitance C.sub.f of the associated LCL filter 3
and represents resistive losses in the LCL filter 3. By way of
example, the converter unit 1 shown in FIG. 1 is a three-phase
unit. It should be mentioned that the converter unit 1 may in
general be any form of converter unit 1 for switching of .gtoreq.2
switching voltage levels (multi-level converter circuit) with
respect to the voltage of a capacitive energy store 9 which is
connected to the converter unit 1, with the capacitive energy store
9 then being formed by any desired number of capacitances, which
are then connected such that they are matched to the appropriately
configured converter circuit element.
In an exemplary method for operation of the converter circuit, the
drivable power semiconductor switches of the conversion unit 1 are
now driven by means of a drive signal S which is formed from
reference voltages u*.sub.1, u*.sub.2, u*.sub.3. A look-up table is
normally used to form the drive signal, in which appropriate drive
signals are permanently associated with reference voltage values,
or a modulator which is based on pulse-width modulation. According
to the disclosure, the reference voltages u*.sub.1, u*.sub.2,
u*.sub.3 are formed from subtraction of damping voltages u.sub.d1,
u.sub.d2, u.sub.d3 from reference-phase connection voltages
u*i.sub.1, u*i.sub.2, u*i.sub.3, with the damping voltages
u.sub.d1, u.sub.d2, u.sub.d3 being formed from filter capacitance
currents i.sub.Cf1, i.sub.Cf2, i.sub.Cf3, which are weighted with a
variable damping factor K.sub.f, of the LCL filters 3, as
illustrated in particular by the following formula.
u.sub.d=K.sub.fi.sub.Cf
The damping voltages u.sub.d1, u.sub.d2, u.sub.d3 are thus
proportional to the filter capacitance currents i.sub.Cf1,
i.sub.Cf2, i.sub.Cf3 and are then subtracted from the
reference-phase connection voltages u*.sub.i1, u*.sub.i2,
u*.sub.i3, which corresponds to the connection of a damping
resistor to each phase connection 2 of the converter unit 1. This
advantageously allows active damping of distortion, that is to say
undesirable oscillations, in the filter output currents i.sub.fg1,
i.sub.fg2, i.sub.fg3 and filter output voltages u.sub.g1, u.sub.g2,
u.sub.g3, that this distortion is greatly reduced and, in the ideal
case is very largely suppressed. Furthermore, there is no need for
connection of discrete, very space-consuming damping resistors,
which are complex to implement and are therefore expensive to the
respective phase connection in order to allow effective damping of
the undesirable distortion.
The damping factor K.sub.f can be set such that the undesirable
oscillations of the filter output voltages u.sub.g1, u.sub.g2,
u.sub.g3 or of phase-connection voltages, e.g., harmonics, are just
not amplified.
As shown in FIG. 1, an exemplary apparatus for carrying out an
exemplary method for operation of a converter circuit for this
purpose has a regulation device 4, which is used to produce the
reference voltages u*.sub.1, u*.sub.2, u*.sub.3 and is connected
via a drive circuit 5 for formation of the drive signal S to the
drivable power semiconductor switches. By way of example, the drive
circuit 5 has a look-up table in which appropriate drive signals
are permanently associated with reference-voltage values, or a
modulator which is based on pulse-width modulation. According to
the disclosure, the regulation device 4 has a first calculation
unit 6 for formation of reference voltages u*.sub.1, u*.sub.2,
u*.sub.3 from the subtraction of damping voltages u.sub.d1,
u.sub.d2, u.sub.d3 from reference-phase connection voltages
u*.sub.i1, u*.sub.i2, u*.sub.i3, with the first calculation unit 6
being supplied with reference-phase connection voltages u*.sub.i1,
u*.sub.i2, u*.sub.i3 and, in order to form the damper voltages
u.sub.d1, u.sub.d2, u.sub.d3, filter capacitance currents
i.sub.Cf1, i.sub.Cf2, i.sub.Cf3 of the LCL filters 3. As shown in
FIG. 1, the filter capacitance currents i.sub.Cf1, i.sub.Cf2,
i.sub.Cf3 are measured by appropriate measurement devices.
Furthermore, the regulation device 4 has a regulation unit 7 for
production of the reference-phase connection voltages u*.sub.i1,
u*.sub.i2, u*.sub.i3. The exemplary apparatus for carrying out the
method for operation of the converter circuit can accordingly be
produced very easily and cost-effectively, since the circuit
complexity can be kept extremely low and, furthermore, only a small
number of components are required to construct it. This apparatus
allows the exemplary method to be carried out particularly
easily.
It has been found to be advantageous for the filter capacitance
currents i.sub.Cf1, i.sub.Cf2, i.sub.Cf3 to be filtered by means of
a high-pass filter. This means that the damping voltages u.sub.d1,
u.sub.d2, u.sub.d3 are formed only from harmonics of the filter
capacitance currents i.sub.Cf1, i.sub.Cf2, i.sub.Cf3, in particular
higher-frequency harmonics of the filter capacitance currents
i.sub.Cf1, i.sub.Cf2, i.sub.Cf3, and the variable damping factor
K.sub.f, so that the active damping can advantageously act only on
the harmonics in the filter output currents i.sub.fg1, i.sub.fg2,
i.sub.fg3 and filter output voltages u.sub.g1, u.sub.g2, u.sub.g3.
High-pass filtering of the filter capacitance currents i.sub.Cf1,
i.sub.Cf2, i.sub.Cf3 is carried out by a high-pass filter which is
connected between the measurement devices for measurement of the
filter capacitance currents i.sub.Cf1, i.sub.Cf2, i.sub.Cf3 and the
first calculation unit 6, with the high-pass filter not being shown
in FIG. 1, for clarity reasons.
The reference-phase connection voltages u*.sub.i1, u*.sub.i2,
u*.sub.i3 are formed from a d-component of the Park-Clarke
transformation (produced by regulation of the dc voltage u.sub.dc
of a capacitive energy store 9 which is connected to the converter
unit 1 at a dc voltage reference value u*.sub.dc of reference-phase
connection currents i*.sub.fid and from a predeterminable
q-component of the Park-Clarke transformation of the
reference-phase connection currents i*.sub.fiq. The regulation can
be carried out using a proportional-integral characteristic. As
shown in FIG. 1, the regulator unit 7 for regulation of the dc
voltage u.sub.dc of the capacitive energy store 9 at the dc voltage
reference value u*.sub.dc has a first proportional-integral
regulator 8, to whose input the difference between the dc voltage
(u.sub.dc) of the capacitive energy store 9 and the dc voltage
reference value u*.sub.dc is supplied, and at whose output the
d-component of the Park-Clarke transformation of the
reference-phase connection currents i*.sub.fid is produced.
The Park-Clarke transformation is in general defined as:
x=(x.sub.d+jx.sub.q)e.sup.j.omega.t using the variables illustrated
in FIG. 1: .sub.g=u.sub.g1+u.sub.g2e.sup.jy+u.sub.g3e.sup.j2y
.sub.fi=i.sub.fi1+i.sub.fi2e.sup.jy+i.sub.fi3e.sup.j2y
.sub.Cf=i.sub.Cf1+i.sub.Cf2e.sup.jy+i.sub.Cf3e.sup.j2y
.sub.fg=i.sub.fg1+i.sub.fg2e.sup.jy+i.sub.fg3e.sup.j2y where
y=2.pi./3, where x is a complex variable, x.sub.d is the
d-component of the Park-Clarke transformation of the variable x and
x.sub.q is the q-component of the Park-Clarke transformation of the
variable x All of the Park-Clarke transformations of variables
which have already been mentioned and those which will be mentioned
in the following text are produced using the formula quoted above.
The Park-Clarke transformation advantageously transforms not only
the fundamental of the complex variable x, but also all of the
harmonics that occur of the complex variable x.
The regulation device 4 shown in FIG. 1 has a third calculation
unit 16 for formation of the d-component of the Park-Clarke
transformation of the filter output voltages u.sub.gd, of the
q-component of the Park-Clarke transformation of the filter output
voltages u.sub.gq and of the fundamental angle .omega.t of the
filter output voltages u.sub.g1, u.sub.g2, u.sub.g3, with the input
side of the third calculation unit 16 being supplied with the
filter output voltages u.sub.g1, u.sub.g2, u.sub.g3 of the LCL
filters 3. The third calculation unit 16 can be a phase locked
loop, in which case the Park-Clarke transformations of the
individual variables are carried out using the definitions given
above.
Furthermore, the d-component of the Park-Clarke transformation of
the reference-filter output voltages u*.sub.gd is produced by
regulation of the d-component of the Park-Clarke transformation of
the phase connection current i.sub.fid at the sum of the
d-component of the Park-Clarke transformation of the
reference-phase connection currents i*.sub.fid and a d-component of
the Park-Clarke transformation of at least one harmonic of filter
output currents i*.sub.fghd with respect to the fundamental of the
filter output currents i.sub.fg1, i.sub.fg2, i.sub.fg3. The
regulation can be carried out using a proportional-integral
characteristic. Furthermore, the q-component of the Park-Clarke
transformation of the reference filter output voltages u*.sub.gq is
produced by regulation of the q-component of the Park-Clarke
transformation of the phase connection currents i.sub.fiq at the
sum of the q-component of the Park-Clarke transformation of the
reference-phase connection currents i*.sub.fiq and a q-component of
the Park-Clarke transformation of at least one harmonic of the
filter output currents i*.sub.fghq with respect to the fundamental
of the filter output currents i.sub.fg1, i.sub.fg2, i.sub.fg3. The
regulation can be carried out using a proportional-integral
characteristic. The index h of the d-component and the q-component
of the Park-Clarke transformation of a harmonic of the filter
output currents i*.sub.fghd i*.sub.fghq represents the h-th
harmonic of these variables, where h=1, 2, 3, . . . The additional
variables introduced in the following text with the index h
likewise use the index h for the h-th harmonic of the associated
variable, h=1, 2, 3, . . . As shown in FIG. 1, the regulator unit 7
for regulation of the d-component of the Park-Clarke transformation
of the phase connection currents i.sub.fid at the sum of the
d-component of the Park-Clarke transformation of the reference
phase connection currents i*.sub.fid and a d-component of the
Park-Clarke transformation of at least one harmonic of the filter
output currents i*.sub.fghd with respect to the fundamental of the
filter output currents i.sub.fg1, i.sub.fg2, i.sub.fg3 has a second
proportional-integral regulator 10 to whose input side the
difference between the sum of the d-component of the Park-Clarke
transformation of the reference-phase connection currents
i*.sub.fid and a d-component of the Park-Clarke transformation of
at least one harmonic of the filter output currents i*.sub.fghd
with respect to the fundamental of the filter output currents
i.sub.fg1, i.sub.fg2, i.sub.fg3 and the d-component of the
Park-Clarke transformation of the phase connection currents
i.sub.fid are supplied, and on whose output side the d-components
of the Park-Clarke transformation of the reference-filter output
voltages u*.sub.gd is produced. Furthermore, for regulation of the
q-component of the Park-Clark transformation of the phase
connection currents i.sub.fiq at the sum of the q-component of the
Park-Clarke transformation of the reference phase connection
currents i*.sub.fiq and the q-component of the Park-Clarke
transformation of at least one harmonic of the filter output
currents i*.sub.fghq with respect to the fundamental of the filter
output currents i.sub.fg1, i.sub.fg2 i.sub.fg3, the regulator unit
7 has a third proportional-integral regulator 11 to whose input
side the difference between the sum of the q-component of the
Park-Clarke transformation of the reference phase connection
currents i*.sub.fiq and a q-component of the Park-Clarke
transformation of at least one harmonic of the filter output
currents i*.sub.fghq with respect to the fundamental of the filter
output currents i.sub.fg1, i.sub.fg2, i.sub.fg3 and the
q-components of the Park-Clarke transformation of the phase
connection currents i.sub.fiq are supplied, and on whose output
side the q-component of the Park-Clarke transformation of the
reference-filter output voltages u*.sub.gq is produced.
Furthermore, the d-component of the Park-Clarke transformation of
the reference-phase connection voltages u*.sub.id is produced by
the sum of the d-component of the Park-Clarke transformation of the
reference filter output voltages u*.sub.gd and the d-component of
the filter output voltages u.sub.gd and a d-component of the
Park-Clarke transformation of at least one harmonic of the filter
output voltages u*.sub.ghd. In addition the q-component of the
Park-Clarke transformation of the reference-phase connection
voltages u*.sub.iq is produced by the sum of the q-component of the
Park-Clarke transformation of the reference-filter output voltages
u*.sub.gq and the q-component of the Park-Clarke transformation of
the filter-output voltages u.sub.gq and a q-component of the
Park-Clarke transformation of at least one harmonic of the filter
output voltages u*.sub.ghq. In order to produce the d-component of
the Park-Clarke transformation of the reference-phase connection
voltages u*.sub.id, the regulator unit 7 has a first adder 12, to
which the d-component of the Park-Clarke transformation of the
reference filter output voltages u*.sub.gd, the d-component of the
filter output voltages u.sub.gd and the d-component of the
Park-Clarke transformation of at least one harmonic of the filter
output voltages u*.sub.ghd are supplied. In addition, in order the
produce the q-component of the Park-Clarke transformation of the
reference phase connection voltages u*.sub.iq, the regulator unit 7
has, as shown in FIG. 1, a second adder 13, to which the
q-component of the Park-Clarke transformation of the
reference-filter output voltages u*.sub.gq, the q-component of the
Park-Clarke transformation of the filter output voltages u.sub.gq
and the q-component of the Park-Clarke transformation of at least
one harmonic of the filter output voltages u*.sub.ghq are
supplied.
In order to form the d-component of the Park-Clarke transformation,
as has already been mentioned above, of at least one harmonic of
the filter output currents i*.sub.fghd with respect to the
fundamental of the filter output currents i.sub.fg1, i.sub.fg2,
i.sub.fg3, the q-component of the Park-Clarke transformation of at
least one harmonic of the filter output currents i*.sub.fghq with
respect to the fundamental of the filter output currents i.sub.fg1,
i.sub.fg2, i.sub.fg3, the d-component of the Park-Clarke
transformation of the at least one harmonic of the reference filter
output voltages u*.sub.ghd and the q-component of the Park-Clarke
transformation of the at least one harmonic of the reference-filter
output voltages u*.sub.ghq the regulation unit 4 has a second
calculation unit 15, as shown in FIG. 1. As shown in FIG. 1, the
input side of the second calculation unit 15 is supplied with the
d-component with the filter output voltages u.sub.gd, the
q-component of the filter output voltages u.sub.gq, the phase
connection currents i.sub.fi1, i.sub.fi2, i.sub.fi3, the filter
capacitance currents i.sub.Cf1, i.sub.Cf2, i.sub.Cf3 and the
fundamental angle .omega.t of the filter output voltages u.sub.g1,
u.sub.g2, u.sub.g3. In order to illustrate the formation of the
individual variables in the calculation unit 15, FIG. 2 shows one
exemplary embodiment of the second calculation unit 15, in which
the input variables shown in FIG. 2 are obtained using the
following formula:
i.sub.fghd+ji.sub.fghq=i.sub.fihd+ji.sub.fihq-(i.sub.Cfhd+ji.sub.Cfhg)
with the d-components of the Park-Clarke transformation and the
q-components of the Park-Clarke transformation being obtained by
applications of the Park-Clarke transformation to the measured
phase connection currents i.sub.fi1, i.sub.fi2, i.sub.fi3 including
the associated harmonics, and filter capacitance currents
i.sub.Cf1, i.sub.Cf2, i.sub.Cf3 including the associated harmonics.
This Park-Clarke Clarke transformation is carried out in particular
in the second calculation unit 15, although this is not illustrated
in the second calculation unit 15 shown in FIG. 2, for clarity
reasons.
Finally, the reference-phase connection voltages u*.sub.i1,
u*.sub.i2, u*.sub.i3 are produced by an inverse Park-Clarke
transformation of the d-component of the Park-Clarke transformation
of the reference-phase connection voltages u*.sub.id and the
q-component of the Park-Clarke transformation of the
reference-phase connection voltages u*.sub.iq. As shown in FIG. 1,
the regulator unit 7 for this purpose has a calculation unit 14 for
formation of the reference-phase connection voltages u*.sub.i1,
u*.sub.i2, u*.sub.i3 by inverse Park-Clarke transformation, to
whose input side the d-component of the Park-Clarke transformation
of the reference-phase connection voltages u*.sub.id and the
q-component of the Park-Clarke transformation of the
reference-phase connection voltages u*.sub.iq are supplied.
In order to illustrate an exemplary method of operation of the
active damping based on the exemplary method as explained above,
FIG. 3 shows a waveform of the filter output currents i.sub.fg1,
i.sub.fg2, i.sub.fg3 in which undesirable oscillations in the
filter output currents i.sub.fg1, i.sub.fg2, i.sub.fg3 are actively
damped, so that this distortion is greatly reduced. A further
improvement in the reduction of harmonics is shown in a waveform of
the filter output currents i.sub.fg1, i.sub.fg2, i.sub.fg3 in FIG.
4 with active damping, and additional active reduction of harmonics
using the exemplary method as described above.
It should be mentioned that all of the steps of the exemplary
method may be implemented in the form of software, which can then
be loaded and then run for example on a computer system, in
particular with a digital signal processor. The digital delay times
which occur in systems such as this, in particular for the
calculations, may be in general be taken into account, for example,
by addition of an additional term to the fundamental angle .omega.t
in the Park-Clarke transformation. Furthermore, the exemplary
apparatus, as described in detail above, can also be implemented in
a computer system, in particular in the digital signal
processor.
Overall, it has been possible to show that the exemplary apparatus,
e.g., as shown in FIG. 1, for carrying out the exemplary method for
operation of the converter circuit can be implemented very easily
and cost-effectively, since the circuit complexity is extremely low
and, furthermore, only a small number of components are required to
construct it. This exemplary apparatus therefore makes it possible
to carry out the exemplary method particularly easily.
It will be appreciated by those skilled in the art that the present
invention can be embodied in other specific forms without departing
from the spirit or essential characteristics thereof. The presently
disclosed embodiments are therefore considered in all respects to
be illustrative and not restricted. The scope of the invention is
indicated by the appended claims rather than the foregoing
description and all changes that come within the meaning and range
and equivalence thereof are intended to be embraced therein.
LIST OF REFERENCE SYMBOLS
1 Converter unit 2 Phase connection of the converter unit 3 LCL
filter 4 Regulation device 5 Drive circuit 6 First calculation unit
of the regulation device 7 Regulator unit 8 First
proportional-integral regulator 9 Capacitive energy store 10 Second
proportional-integral regulator 11 Third proportional-integral
regulator 12 First adder 13 Second adder 14 Calculation unit for
the regulator unit 15 Second calculation unit of the regulation
device 16 third calculation unit of the regulation device
* * * * *